What is the difference between the particles は and が?
I know, I know, は is the topic particle and が is the subject particle, but what exactly is the difference, semantically, between the topic and the subject?
An easy way to understand it is to insert "as for A" or "regarding A" when 「Aは」 is used and "it is B that" when 「Bが」 is used.
A phrase like the one mentioned in one of the other posts 私はコーヒーが好きです。becomes: As for me, it is coffee that is likable. Of course that would be a really bad translation, but it is a good way to get the meaning and then find the best equivalent in English to express the same idea, in this case: I like coffee.